The present apparatus relates to a motor operator, and, more particularly, to a motor operator for circuit breakers.
The use of motor operators (motor charging mechanisms) to allow the motor-assisted operation of electrical circuit breakers is well known. A motor operator is typically secured to the top of a circuit breaker housing. A linkage system within the motor operator mechanically interacts with a circuit breaker operating handle, which extends from the circuit breaker housing. The linkage system is operatively connected to a motor within the motor operator and a powerful closing spring. The motor drives the linkage system, which, in turn, moves the operating handle to reset/open and charge the closing spring the circuit breaker. The operating handle is moved from off to on by releasing the stored energy in the closing spring which quickly drives the linkage system and handle to turn on the circuit breaker between xe2x80x9conxe2x80x9d, xe2x80x9coffxe2x80x9d, and xe2x80x9cresetxe2x80x9d positions, depending on the rotational direction of the motor.
When the handle is moved to the xe2x80x9conxe2x80x9d position, electrical contacts within the circuit breaker are brought into contact with each other, allowing electrical current to flow through the circuit breaker. When the handle is moved to the xe2x80x9coffxe2x80x9d position, the electrical contacts are separated, stopping the flow of electrical current through the circuit breaker. When the handle is moved to the xe2x80x9cresetxe2x80x9d position, an operating mechanism within the circuit breaker is reset, as is necessary after the operating mechanism has tripped in response to an overcurrent condition in the electrical circuit being protected by the circuit breaker.
Electric circuit breakers of relatively high current carrying capacity utilize large movable contact arm assemblies to carry the current. Moreover, substantial contact pressure is exerted on the movable contact arms by powerful springs in order to achieve intimate electrical contact between the stationary and movable contacts of the rotary circuit breakers. These powerful springs are also used for abrupt separation of the contacts.
When using a motor operator to open or close a circuit breaker, it is desirable to close the circuit breaker contacts as quickly as possible for certain applications. To accomplish this, motor operators typically employ a large closing spring that, when released, can move the operating handle of the circuit breaker from off to on within the required time. Such motor operators must be large in size to contain the large spring and operating mechanism required to move the breaker handle from the off to the on position.
A motor operator must also be designed to prevent damage to the circuit breaker, and to itself, when moving the circuit breaker handle between the reset, off and on positions. In particular, the motor operator and the circuit breaker must be designed such that closing the circuit does not damage the circuit breaker operating mechanism. This is typically achieved by strengthening the motor operator and the circuit breaker so that they may withstand the stress caused by overtravel, or by utilization of limit switches, takeup springs and solenoids to disengage the motor after the handle has reached a desired point. While effective, the use of limit switches, takeup springs and solenoids to disengage the motor requires the use of many components and, therefore, increases the cost of the motor operator and its potential for failure.
These and other drawbacks are overcome by a motor operator mechanism for moving a breaker handle of a circuit breaker between off and on positions. The motor operator mechanism comprising: a first pin biased to engage the breaker handle in a direction to close the circuit breaker; a pin latch configured to releasably engage the first pin when the breaker handle is in a position intermediate to the off and on positions, wherein releasing the pin latch allows the first pin to move the breaker handle to the on position.